With the implementation of China's western development strategy, the height and size of the earth rock cofferdam has increased year by year. Due to the convenience and economy of the construction, inclined wall type composite geomembranes are employed in many cofferdams. As the technical difficulty of high rockfill cofferdam increases with the increasing cofferdam scale, at joints of the composite geomembranes and the shoreside toe slabs or connections of the composite geomembranes and impervious walls, due to water pressure and gravity, the cofferdams are integrally deformed and produce a relative displacement from the rigid connection. Moreover, this relative displacement is only taken by the composite geomembranes in extremely small area around the connections. If the expansion joints are disposed improperly, the composite geomembranes will produce obvious strain, and then the tensile or shear failure occurs. The failure phenomenon has been observed during running or removing of a number of earth rock cofferdams, connections between the composite geomembranes and the shoreside toe slabs or joints between the composite geomembranes and the concrete caps on the top of the impervious walls are damaged at different extents. The failure mechanism has been proved by centrifugal model test and numerical calculation.
At the connections between the composite geomembranes and shoreside toe slabs as well as the connections between composite geomembranes and impervious walls, because the composite geomembranes are paved on granular padding materials with lower modulus, a larger relative shift occurs compared to the rigid connections. In the past, many projects have dispoosed expansion joints in the connection area, but the expansion joints are simply compacted by overlying rock filling materials and water loading to work out.